Anion receptors comprising a plurality of quaternary amine groups are known. Examples of such compounds may be seen in P.G. Potvin and J-M Lehn, Prog. Macrocyclic Chem., 1987, 3, 214.
L .A. Summers, "The Bipyridinium Herbicides", Academic Press, New York, 1980, describes the use of certain compounds comprising diquaternary 2,2'-bipyridinium moieties in herbicidal applications.
Metal ion centres have also been utilised in systems for the recognition of anions as described in D.N. Reinhoudt, J. Am. Chem. Soc. 1992, 114, 9671-9673.